What is a circular linked list?

#include "Clinkedlist.h"

circularLinkedList::circularLinkedList()
{
    head = NULL;
}

bool circularLinkedList::addElement(int element)
{
    //creating node
    node* newNode = new node;
    newNode->data = element;
    newNode->next = NULL;

    //first element
    if (!head)
    {
        head = newNode;
        head->next = newNode;
        return true;
    }

    //variable to find end of linked list
    node* dummy = head;

    //finding last element of linked list
    do
    {   
        //ensures that same element is not added twice
        if (dummy->data == element)
        {
            return false;
        }

        dummy = dummy->next;

    } while (dummy->next != head);

    dummy->next = newNode;
    newNode->next = head;

    return true;
    
}

bool circularLinkedList::deleteElement(int element)
{
    //if list is empty
    if (!head)
    {
        return false;
    }

    //variables to find the element to delete
    node* prev_dummy = head;
    node* curr_dummy = head->next;

    if(prev_dummy == curr_dummy)
    {
        if (curr_dummy->data == element)
        {
            delete head;
            head = NULL;
            return true;
        }
        return false;
    }

    do
    {
        //deleting data
        if(curr_dummy->data == element)
        {
            if (curr_dummy == head)
            {
                head = curr_dummy->next;
            }
            prev_dummy->next = curr_dummy->next;
            delete curr_dummy;
            return true;
        }

        prev_dummy = prev_dummy->next;
        curr_dummy = curr_dummy->next;

    } while (prev_dummy != head);

    return false;
}

void circularLinkedList::display()
{
    //variable to traverse linked list
    node* dummy = head;

    do
    {
        std::cout << "data: " << dummy->data << endl;
        dummy = dummy->next;
    } while (dummy!= head);
}